The hindfoot joint comprises the junctions formed between the cuboid, calcaneus, and the talus. Mobility in these joints is critical to almost all bipedal movement, and even standing. This joint is vulnerable to substantial damage in particular in falls, or in automobile or vehicle crashes.
The present invention is designed in a first aspect for the most common fracture to the hindfoot joint: i.e. calcaneal fractures of which the most common is a Sander's type II fracture. This type of fracture generally comprises an interior to lateral fracture which often results in a three-part fragmentation of the calcaneus often leaving the sustentaculum as the healthiest fragment and displacing laterally and posterior the remaining fragments of the calcaneus. In addition, the plate of the present invention can be used for osteotomies and fixation of other fractures or reconstruction due to trauma or deformities.
Implants have been provided in the past to try to help stabilize the fragments in order to allow the calcaneus to fuse, and these past attempts have generally provided flat plates of a somewhat flexible nature to allow a surgeon to bend the plate before implantation, and/or to allow the plate be drawn into position on the bone to allow for some contouring of the plate as part of the implantation surgery. However, the prior art plates often had elements that extended beyond the bone to irritate soft tissue such as in particular the peroneal ligaments, which often causes irritation if not eruption of the ligament. Further, while the idea of loading a flexible planar plate maybe suitable to allow contouring fixed to healthy bone, it is totally unsuitable for reconstruction or reduction of fractures so as to rebuild a fractured bone. In contrast, an aspect of the present invention provides a fully contoured plate having substantially no planar surfaces (with one small but important exception at a pre-determined origin which permits the plate to be constructed and measured). The contoured plate has a surface that faces the bone which includes radiused sections, one extending inferior to superior which is curved inferior to superior in a shape which is close to cylindrical and which approximates the shape of the cuboid bone. The second radiused section is curved in the vicinity of the anterior strut, and in particular at the inferior portion of the plate, to accommodate the peroneal tubricle.
In addition, the posterior portion or body of the plate is formed to so as to try restore maximal length and height of the calcaneus in reconstruction or reduction of the bone using the plate of the present invention. The anterior portion includes a double eared tab or tail that has upper and lower holes spaced from a central hole in the tab portion to allow for triangular multiplanar fixation. The central portion of the plate includes three fenestrations spanned by two struts extending from the inferior to the superior portions of the plate which has a contour vaguely reminiscent of the outline of a whale where the body segment beginning at the anterior strut curves through a three hole portion that is reinforced to accommodate weight transfer from the tibia to the talus to the calcaneous. The top extends from the posterior strut to the top posterior hole, and includes a translation slot which is an optional point for a surgeon to begin with fixation to the bone. This feature allows the surgeon the ability to translate the plate based on radiographic evidence once the first screw is inserted to better accommodate patient anatomy. The struts are strategically designed to maximize strength and to minimize the possibility of loss of correction through loading in use. The body generally is a blunted ovoid ring (or “whale shaped”) formed of plate segments including holes for fixation screws. The posterior segment of the body extends inferiorly and slightly posteriorly to a central hole and then inferiorly and slightly anteriorly to an inferior posterior hole which has been selected as the origin for plotting of the plate, and which includes a flat counterbore from which the remainder of the plate can be plotted using Cartesian coordinates. From here, the inferior segment of the body of the plate curves slightly upward to accommodate the peroneal ligament. The plate includes holes at the inferior ends of the posterior and the anterior struts so that these struts are supported by the screws as well as the linking portions of the plate and so that the load that is taken up at the opposing ends of the struts is distributed through the struts and to the adjoining portions of the plate. The inferior hole at the anterior strut forms the end of the body of the blunted ovoid ring or “whale outline”, and the tail extends anteriorly with a triangular fenestration and a superior and an inferior ear, both of which include a hole. A third hole is located in this section to maximize the number of screws that can be placed in the anterior process fragment and to allow for triangular fixation in this area. Selected fixation holes in the plate are threaded for use with locking screws. In a particular aspect of the invention there are two locking holes which are internally threaded and are designed to directly support the subtalar joint fragment, specifically just inferior to the posterior facet (i.e. the articulating surface) of the calcaneous. Optionally, the anterior portion can also include locking holes. The corresponding locking screws include mating external locking threads on the head portion. The plate further includes smaller holes which allow the use of K wires both for reduction of the fragments, and for further fixation.
In addition, the present invention provides in a separate aspect, a calcaneal plate having a reinforced portion in the vicinity of the posterior facet. This area is where the majority of the weight transfer from the tibia to the talus to calcaneus occurs. In addition the plate has a hole designed to allow placement of a screw into the sustentaculum to enable the bone to be reduced using the construct as a tool during the surgery as this is an area where subsidence is likely to occur in many fractures or breaks. Preferably the screw is a compression screw, meaning that the screw is partially rather than fully threaded and the threads are on the distil portion with a shaft area that is free from threads. In addition, the calcaneal plate provides a posterior centered superior translation slot, and support struts are provided between the inferior portion and the superior portion of the plate structure. In addition, an anterior portion has a plurality of holes to provide for the possibility to provide a choice to a surgeon who has to deal with that bone, or a bone that has been severally damaged during the trauma.
Finally, the calcaneal plate of the present invention is contoured so as to provide a construct to build the displaced/fractured bone back to, rather than contouring a plate to fit a fractured bone, which is unlikely reduced to its original disposition. Additionally, the plate is shaped to maximum the height, width and general shape that would be supported under the plate in order for a surgeon to regain the original parameters/perimeter of the calcaneus. The design is generally an organic fluid design devoid of sharp edges which in most circumstances would not project beyond the bone. Further, the design has been generalized from a survey of the population in order to provide for the best possibility of the plate being to accommodate a number of variations and individuals.
The plate is provided in a right and a left version and is generally used on the lateral portion of the calcaneal bone situated slightly posterior to the cuboid slightly inferior to the posterior facet, and supported on the posterior portion of the calcaneus. The plate is also provided in multiple profiles for small and large patients.